What causes flatworms?

Flatworms are a type of invertebrate belonging to the phylum Platyhelminthes. They are not caused by any external factors but are a result of evolutionary processes. Flatworms can be found in various environments, including freshwater, marine, and terrestrial habitats, and their characteristics, such as a flattened body shape, are adaptations that have evolved over millions of years for survival and reproduction. Some flatworms are parasitic, while others are free-living, reflecting their diverse ecological roles.